This invention pertains to apparatus for removing tissue forming blockages and constrictions in arteries, and more particularly, to apparatus for cutting and removing scar and other tissue accumulated inside stents within an artery.
Material known as plaque accumulates inside arteries, and can form a constriction, or stenosis, that blocks blood flow within the arteries. If this occurs within the coronary artery, blood flow can be obstructed in the coronary artery, thereby resulting in a heart attack, and perhaps death. Accordingly, much attention has been devoted to methods and apparatus for unblocking arteries clogged with plaque deposits.
One method for removing an obstruction in an artery is angioplasty. During angioplasty, a physician (typically a cardiologist) inserts a catheter into the patient's coronary artery. There is a balloon at the distal end of the catheter. The cardiologist inflates the balloon, thereby expanding the arterial lumen. The balloon is then deflated and the catheter is removed. Examples of angioplasty catheters are described in U.S. Pat. No. 4,323,071, issued to Simpson et al. and U.S. Pat. No. 5,769,868 issued to Yock et al.
Another method for removing an obstruction is to insert a stent in the patient's artery. A stent is a mechanical device inserted into an obstructed portion of a patient's artery which pushes the artery walls outwardly to increase the artery lumen size. Unlike a balloon catheter, a stent is typically not removed from the patient's artery after insertion. Rather, the stent remains in place to ensure that the lumen retains an appropriate caliber. FIG. 1A schematically illustrates in cross section an artery 10 with a lesion comprising atherosclerotic plaque 11, and stent 12 placed therein to maintain the desired caliber of the artery lumen. Examples of stents are discussed in U.S. Pat. No. 4,830,003, issued, to Wolff et al., U.S. Pat. No. 5,618,299 issued to Khosravi, et al., and U.S. Pat. No. 5,549,662 issued to Fordenbacher.
Unfortunately, scar tissue (e.g. tissue 14 of FIG. 1B) can accumulate within the interior of stent 12 after stent 12 is in place, thereby obstructing the artery lumen. Such tissue is typically smooth, has a consistent morphology, and deposits circumferentially at the site where stent 12 has been implanted. This tissue can block the artery and cause serious health problems, including death. Accordingly, it would be desirable to remove the tissue that accumulates within the stent.